BAE Systems is to cut jobs in the UK and Australia after warning that earnings would be slightly lower than expected as the defence company reduced the rate of producing Eurofighter Typhoon aircraft.

BAE said it planned to cut 371 UK roles in its military air and information business as a result of reduced production of the Typhoon, the multirole fighter aircraft. Typhoon sales will fall from about £1.3bn this year to £1.1bn in 2016, BAE said in a trading update.

Almost all the cuts will be at BAE’s detailed manufacturing operation at Samlesbury, Lancashire, with some at its assembly plant in Warton, also in Lancashire. The military air and information business employs about 13,000 people in the UK.

Ian King, BAE’s chief executive, said compulsory reduncies might be necessary in the UK but that overall the company was hiring more people, including graduates and apprentices.

“I’m not suggesting any of this is anything but really difficult for the people involved and I take it very seriously but this is a company with 13,000 people in military air and information and 30,000 employed in the UK.”

The Unite union warned BAE that cutting jobs too quickly could lead to skills shortages and called on the government to help the company win export orders.

Unite’s national officer, Ian Waddell, said: “This is disappointing news on top of a miserable few weeks for manufacturing in the UK. The government needs to stop dithering and act urgently to stop the haemorrhage of skilled UK manufacturing jobs.”

King said the cuts were needed despite a generally positive outlook for BAE’s business amid international tensions and fears about cyber-security, on which the company advises companies and governments.

“The nature of the world at the moment is a very unsafe place,” King said. “The Conservative government have made it very clear they are committed to defence and security and the US has just increased its budget. There is a lot of operational activity going on in a lot of places in the world. This is a very unsafe and unsecure environment.”

In Australia, the company said that with no near-term prospect of work beyond existing ship orders it would cut 150 jobs at its Williamstown shipyard in Melbourne and consolidate its operating divisions from three to two to reduce management costs.

BAE cut 200 jobs at Williamstown in August, reducing headcount to 350 from a peak of 1,100 in October 2014. The company said that if no new work came in it would close the site in the first quarter of 2016 with an additional 150 job losses. BAE will take a charge this year to write down most of the value of the shipyard.

BAE’s shares were the bigger gainers in the FTSE 100 index on Thursday, closing up nearly 4% at 455p.

The company said that including a benefit of 2p from tax provisions, it expected underlying earnings per share for 2015 of around 38p – the same level as in 2014 and slightly down from an earlier forecast. The job cuts and writedown at Williamstown would cost up to £120m, accounting for the reduction in earnings guidance.

BAE said overall it expected good sales growth in 2015 and confidence in its prospects was underpinned by a strong order backlog at the half-year of £37.3bn.